Broad-beam imaging

ABSTRACT

Methods of probing a material under investigation using an ultrasound beam. Echolocation data is generated using a multi-dimensional transform capable of using phase and magnitude information to distinguish echoes resulting from ultrasound beam components produced using different ultrasound transducers. Since the multi-dimensional transform does not depend on using receive or transmit beam lines, a multi-dimensional area can be imaged using a single ultrasound transmission. In some embodiments, this ability increases image frame rate and reduces the amount of ultrasound energy required to generate an image.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation and claims the priority benefit ofU.S. patent application Ser. No. 10/759,558 entitled “Broad Beam ImagingMethods,” filed Jan. 16, 2004, now U.S. Pat. No. 7,238,157, which is acontinuation and claims the priority benefit of U.S. patent applicationSer. No. 10/211,391 entitled “Broad-Beam Imaging,” filed Aug. 1, 2002,now U.S. Pat. No. 6,685,645, which claims the priority benefit of U.S.provisional patent application No. 60/370,632 entitled “Broad-BeamImaging,” filed Apr. 5, 2002; U.S. patent application Ser. No.10/211,391 is also a continuation-in-part and claims the prioritybenefit of U.S. patent application Ser. No. 10/039,922 entitled “BlockSwitching in Ultrasound Imaging,” filed Oct. 20, 2001, now U.S. Pat. No.6,773,399; U.S. patent application Ser. No. 10/211,391 is also acontinuation-in-part and claims the priority benefit of U.S. patentapplication Ser. No. 10/039,862 entitled “Simultaneous Multi-Mode andMulti-Band Ultrasonic Imaging,” filed Oct. 20, 2001, now U.S. Pat. No.6,896,658; U.S. patent application Ser. No. 10/211,391 is also acontinuation-in-part and claims the priority benefit of U.S. patentapplication Ser. No. 10/039,910 entitled “Ultrasound System withCableless Coupling Assembly,” filed Oct. 20, 2001, now U.S. Pat. No.6,936,008, which is a continuation-in-part and claims the prioritybenefit of U.S. patent application Ser. No. 09/860,209 entitled“Miniaturized Ultrasound Apparatus and Method,” filed on May 18, 2001,now U.S. Pat. No. 6,569,102, which is a continuation and claims thepriority benefit of U.S. patent application Ser. No. 09/378,175 entitled“Miniaturized Ultrasound Apparatus and Method,” filed on Aug. 20, 1999,now U.S. Pat. No. 6,251,073. The subject matter of these applications isincorporated herein by reference.

This application is related to U.S. Pat. No. 6,866,631 for a “System forPhase Inversion Ultrasonic Imaging” and U.S. Pat. No. 6,663,567 for a“System and Method for Post-Processing Ultrasound Color DopplerImaging.” The subject matter of these commonly owned and related patentsis hereby incorporated by reference.

BACKGROUND

1. Field of the Invention

The invention is in the field of imaging and more specifically in thefield of ultrasonic imaging.

2. Description of the Related Art

Ultrasonic imaging is a method of analysis used for examining a widerange of materials. The method is especially common in medicine becauseof its relatively non-invasive nature, low cost, and fast responsetimes. Typically, ultrasonic imaging is accomplished by generating anddirecting an ultrasound beam into a material under investigation in atransmit phase and observing reflections generated at the boundaries ofdissimilar materials in a receive phase. For example, in medicalapplications observed reflections are generated at boundaries between apatient's tissues. The observed reflections are converted to electricalsignals (channel data) by receiving devices (transducers) and processed,using methods known in the art, to determine the locations of echosources. The resulting data is displayed using a display device such asa monitor.

The prior art processes of producing an ultrasound beam and analyzingresulting echoes is called “beam forming.” The production processoptionally includes defining “transmit” beam characteristics throughaperture apodization, steering, and/or focusing. The analysis processoptionally includes calculating a “receive beam” wherein received echoesare processed to isolate those echoes generated along a narrow region.This calculation includes the identifying one-dimensional line alongwhich echoes are assumed to have been generated, and is thereforereferred to herein as “echo line calculation.” Through beam forming aone-dimensional set of echolocation data is generated using eachtransmit and/or receive beam. Echolocation data is positional datarelating to the physical location of one or more echo source andoptionally includes intensity, velocity and/or similar physicalinformation. Echolocation data may include post-beam forming raw data,detected data, or image data. Multidimensional echolocation data, suchas an ultrasound image, is generated by scanning a field of view withinthe material under investigation using multiple transmit and/or receivebeams.

The ultrasound beam transmitted into the material under investigationduring the transmit phase is generated by applying electronic signals toa transducer. The ultrasound beam may be scattered, resonated,attenuated, and/or reflected as it propagates through the material underinvestigation. A portion of the reflected signals are received attransducers and detected as echoes. The receiving transducers convertthe echo signals to electronic signals and optionally furnish them to anecho line calculator (beam former) that performs the echo linecalculation inherent to analysis using a receive beam.

After beam forming, an image scan converter uses the calculatedecholocation data to generate image data. In prior art systems the imageformation rate (the frame rate) is limited by at least the total pulsereturn times of all ultrasound beams used to generate each image. Thepulse return time is the time between the transmission of the ultrasoundbeam into the material under investigation and the detection of the lastresulting reflected echoes. The limited frame rate may result intemporal artifacts caused by relative movement between the ultrasoundsystem and a material under investigation.

FIG. 1 shows a prior art ultrasound system, generally designated 100.Ultrasound system 100 includes an element array 105 of transducerelements 110, a backing material 120, an optional matching layer 130, atransmit/receive switch 140 and a beam transmitter 150. Backing material120 is designed to support element array 105 and dampen any ultrasoundenergy that propagates toward backing material 120. Matching layer 130transfers ultrasound energy from transducer elements 110 into thematerial under investigation (not shown). Transducer elements 110,include individual transducer elements 110A-110H individually coupled byconductors 115 and 117, through transmit/receive switch 140, to a beamtransmitter 150. Transmit/receive switch 140 may include a multiplexer145 that allows the number of conductors 117 to be smaller than thenumber of conductors 115. In the transmit phase, beam transmitter 150generates electronic pulses that are coupled through transmit/receiveswitch 140, applied to some or all of transducer elements 110A-110H, andconverted to ultrasound pulses 160. Taken together, ultrasound pulses160 form an ultrasound beam 170 that probes the material underinvestigation.

Ultrasound beam 170 may be focused to limit the region in which echoesare generated. When echo sources are restricted to a narrow region thecalculation of echo location data may be simplified by assuming that theecho sources lie along a “transmit line.” With this assumption, the taskof the echo beam calculator is reduced to a problem of determining theposition of an echo source in one dimension. This position isestablished using the return time of the echo. The accuracy of thisassumption and the spacing of transmit lines are significant factors indetermining the resolution of prior art ultrasound systems. Finelyfocused beams facilitate higher resolution than poorly focused beams.Analogous assumptions and consequences are found in analyses involvingcalculated receive beams.

FIG. 2 shows a prior art focusing system in which element array 105 is aphased array configured to focus ultrasound beam 170 by varying thetiming of electronic pulses 210 applied to transducer elements110A-110H. In this system, electronic pulses 210, are generated at beamtransmitter 150 and passed through transmit/receive switch 140.Electronic pulses 210 are delayed using a delay generator (not shown)and coupled to transducer elements 110A-H. Ultrasound beam 170 is formedwhen transducer elements 110A-H convert properly delayed electronicpulses 210 to ultrasound pulses 160 (FIG. 1). Once formed, ultrasoundbeam 170 is directed along a transmit beam line 250 including a focalpoint 230 with a resulting beam waist 240 characterized by a width ofultrasound beam 170. In a similar manner phased excitation of elementarray 105 is used to direct (steer) ultrasound beam 170 in specificdirections. The cross-sectional intensity of ultrasound beam 170 istypically Gaussian around a focal point and includes a maximum alongtransmit beam line 250. The shape of ultrasound beam 170 may depend onaperture apodization.

In a scanning process, ultrasound system 100 sends a series of distinctultrasound beam 170 along another, different transmit beam line 250 toform an image over more than one spatial dimension. A specificultrasound beam 170 is optionally transmitted in severaltransmit/receive cycles before generating another ultrasound beam 170.Between each transmit phase a receive phase occurs, during which echoesare detected. Since each ultrasound beam 170, included in an ultrasoundscan, requires at least one transmit/receive cycle the scanningprocesses may take many times the pulse return time. This pulse returntime, determined by the speed of sound in the material underinvestigation, is a primary limitation on the rate at which prior artultrasound images can be generated. In addition, undesirable temporalanomalies can be generated if transducer elements 110A-110H moverelative to the material under investigation during the scanningprocess.

FIGS. 3A through 3E show a prior art scanning process in a phased array310 of eight transducer elements, designated 110A through 110H. Subsets320A-320E of the eight transducer elements 100A-110H are each used togenerate one of distinct ultrasound beams 170A-170E. For example, FIG.3A shows ultrasound beam 170A formed by subset 320A, includingtransducer elements 110A-110D. The next step in the scanning processincludes forming ultrasound beam 170B using subset 320B includingtransducer elements 110B-110E as shown in FIG. 3B. In this example, atransmit beam line 250B associated with ultrasound beam 170B passesthrough a focal point 230B, which is displaced from a focal point 230Aby a distance typically equal to the width of one transducer element110. As shown by FIGS. 3C through 3E, each subset 320C through 320E,used to produce each ultrasound beam 170C through 170E, is displaced byone transducer element 110 relative to subsets 320B through 320D,respectively. Echoes detected in the receive phase, occurring betweeneach transmit phase, are used to generate echolocation data and theseecholocation data are typically combined to form an image suitable fordisplay. The scan process may be repeated to produce multiple images.

In practice, phased array 310 may include sixty-four, one hundred andtwenty-eight, or more transducer elements 110. The resolution of theecholocation data depends on the aperture and the number of transducerelement 110, and on the degree to which transmit beam line 250accurately represents possible echo sources within ultrasound beam 170.Representation of ultrasound beam 170A-E using beam line 250A-E is anapproximation that determines the resolution of resulting echolocationdata. A poor approximation will limit the resolution of the resultingecholocation data. A maximum width of ultrasound beam 170A-E is,therefore, limited by the desired resolution of the echolocation data.The accuracy of the approximation is a function of distance from focalpoints 230A-E, the approximation being less accurate at furtherdistances.

Common practice includes generating several ultrasound beams withdifferent focal point 230A-E, and using each set of received echoes togenerate data near focal points 230A-E. Prior art data generation may belimited to an area near focal points 230A-E because, at furtherdistances, the transmit beam line 250 approximation may not besufficiently accurate to provide the echolocation data of a desiredresolution. Typically one receive or transmit beam line 250 is generatedfor each transmit/receive cycle. The number of beams required to imagean area is dependent on both the width and depth of the area to beimaged as well as the desired resolution. By using only echoes nearfocal point 230, only a small portion (e.g. <10%) of the total receivedsignal is used, with the remainder of the received signal beingdiscarded. The prior art makes inefficient use of detected signal.Similar disadvantages occur in systems utilizing synthetic receivelines.

In the prior art the area to be covered, transmit beam width, number oftransmit beam 170, and echolocation data resolution are interdependent.The transmit beam width determines the minimum lateral resolution widthof the echolocation data. Since each transmit beam 170 covers only alimited area, a greater number of transmit beam 170 are required toimage a larger area. Use of a greater number of transmit beam 170lengthens the minimum time required to generate an image.

Disadvantages of the prior art, such as an image formation raterestricted by pulse return time and inefficient signal use, haveprevented prior art ultrasound systems from taking full advantage ofadvances in micro-processing power. The prior art endures thesedisadvantages in order to generate images with the highest possibleresolution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art ultrasound system;

FIG. 2 shows a prior art method of focusing an ultrasound beam;

FIGS. 3A through 3E show a prior art scanning process using a phasedarray of eight transducer elements;

FIG. 4 is a flow chart showing an overview of a broad-beam methodaccording to an embodiment of the invention;

FIG. 5 shows a block diagram of a broad-beam system according to anembodiment of the invention;

FIG. 6 is a flow chart showing details of a broad-beam design stepaccording to an embodiment of the invention;

FIG. 7A shows an ultrasound beam generated using a linear transducerarray according to an embodiment of the invention;

FIG. 7B shows an ultrasound beam generated using a curvilineartransducer array according to an embodiment of the invention;

FIG. 7C shows an ultrasound beam that results in an insonified regiongenerated according to an embodiment of the invention;

FIG. 7D shows a plot of ultrasound intensity through a cross-section ofa broad-beam;

FIG. 8 is a flowchart showing details of a transmit step according to anembodiment of the invention;

FIG. 9 is a flowchart showing details of a receive step according to anembodiment of the invention;

FIG. 10 shows stored data arranged in a channel data array according toan embodiment of the invention;

FIG. 11A shows an echolocation data array including a first axisindicating X position and a second axis indicating Y position accordingto an embodiment of the invention;

FIG. 11B shows an alternative embodiment of the echolocation data arrayincluding first axis indicating angle (θ) and second axis indicatingradius (R) according to an embodiment of the invention;

FIG. 12A shows a Cartesian coordinates system including, for thepurposes of illustration, eleven “X” divisions separating data binsaccording to an embodiment of the invention;

FIG. 12B shows a radial coordinate system representing the areainsonified by an ultrasound beam according to an embodiment of theinvention;

FIGS. 13A and 13B show ultrasound propagating from transducer elementsto objects within a material under investigation according to anembodiment of the invention;

FIG. 14 shows channel data produced from echoes according to anembodiment of the invention;

FIG. 15 shows echolocation data generated using the channel data shownin FIG. 14 according to an embodiment of the invention;

FIG. 16 is a flowchart showing a method included in an echo areacalculation according to an embodiment of the invention;

FIG. 17 shows a graph illustrating three alternative apodizationfunctions according to an embodiment of the invention;

FIG. 18 shows ultrasound transmitted from two transducer elements andstriking an ultrasound reflective object;

FIG. 19 shows signals generated by an SCE transducer element stored in achannel data array according to an embodiment of the invention; and

FIG. 20 is a flowchart showing details of an echo area calculation stepaccording to an embodiment of the invention.

SUMMARY OF THE CLAIMED INVENTION

An exemplary embodiment of the present invention discloses a method ofprobing a material under investigation. Through this exemplary method,transducers transmit an ultrasound beam into the material underinvestigation. The ultrasound beam includes components generated by eachtransducer in a plurality of transducers. Echoes are then received, theechoes having been generated by interactions between the ultrasound beamand the material under investigation. A first set of data from thereceived echoes is generated, the first data having values that includephase and magnitude information and that is capable of being associatedwith a time dimension and distributed over at least one spatialdimension. The phase and magnitude information is used to distinguishechoes, among the received echoes, resulting from ultrasound beamcomponents generated by a subset of transducers in the plurality oftransducers. The first data is converted into second data using thedistinguished echoes, the second data having values distributed over atleast one more spatial dimension than the first data.

In an alternative embodiment of the present invention, a method ofprobing a material under investigation includes transmitting oneultrasound beam into the material under investigation; receiving echoesgenerated by interactions between the ultrasound beam and the materialunder investigation; generating first data from the received echoes, thefirst data having a value that includes phase and magnitude informationand that is capable of being associated with time and at least a firstspatial dimension; and transforming a portion of the first data intosecond data using a transform capable of producing second datadistributed over at least a second spatial dimension and a third spatialdimension, the transform using the phase or magnitude information toselect the portion of first data to be transformed.

A further exemplary embodiment for probing a material underinvestigation includes transmitting an ultrasound beam into the materialunder investigation; receiving echoes generated by interactions betweenthe transmitted ultrasound beam and the material under investigation;generating first data using the received echoes, the first data havingvalues capable of being associated with time and a number of positionsin a first spatial dimension, the number of positions being at least 64and the association with the number of positions being independent ofthe association with time. The first data is then transformed intosecond data having values capable of being associated with at least thefirst spatial dimension and a second spatial dimension.

An exemplary method of generating echolocation data is also disclosed.The method includes generating first data by converting echoes intoelectronic signals, the first data having a plurality of values capableof being associated with time and separately capable of being associatedwith a plurality of positions in at least one spatial dimension, theplurality of values including phase and magnitude information.Echolocation data is generated using the first data and a data transformresponsive to the phase or magnitude information, the echolocation datahaving at least one value derived from two or more members of theplurality of values capable of being associated with different positionsin the plurality of positions.

In another exemplary embodiment of the present invention, a method ofprobing a material under investigation includes transmitting at leasttwo overlapping ultrasound beams into the material under investigation.The at least two overlapping ultrasound beams may be displaced in atleast one spatial dimension. Echoes are received, the echoes having beengenerated by interactions between the at least two overlappingultrasound beams and the material under investigation. Data is generatedfrom the received echoes, the data having a value that includesmagnitude and phase information and is capable of being associated withthe at least one spatial dimension. The generated data from the receivedechoes is combined prior to receive beam formation. The combining mayinclude adjusting the magnitude and phase of the generated data.

An exemplary method of probing a material under investigation is alsodisclosed. Through the method, at least two overlapping ultrasound beamsinto the material under investigation at transmitted, the at least twooverlapping ultrasound beams being displaced in at least one spatialdimension. Echoes generated by interactions between the at least twooverlapping ultrasound beams and the material under investigation arereceived and data from the received echoes is generated. The data mayhave a value that includes magnitude and phase information and iscapable of being associated with the at least one spatial dimension.Receive beam formation is performed, wherein identical receive beams areformed from the at least two overlapping ultrasound beams. The generateddata is combined from the received echoes subsequent to receive beamformation. The combining may include adjusting the magnitude and phaseof the generated data.

An exemplary ultrasound imaging system is also disclosed. The systemincludes a control device for receiving a user indication of therequirements of analysis of a material under investigation. The controldevice then determines a number and shape of ultrasound beams forimaging of the material under investigation in accordance with the userindication. A transducer array then transmits ultrasound beamscorresponding to the number and shape of ultrasound beams determined bythe control device into the material under investigation; echoesproduced by the transmitted ultrasound beams are detected and analogchannel data responsive to the detected echoes is generated. Amulti-channel analog-to-digital converter then generates digital channeldata, the digital channel data including amplitude and phaseinformation. The digital channel data is stored in a channel databuffer. A signal processor then generates multidimensional echolocationdata through transformation of at least the amplitude and phaseinformation of the stored digital channel. The multidimensionalecholocation data may be generated without using transmit, receive, orscan lines. An echolocation data array that includes a pre-selectedcoordinate system stores the generated multidimensional echolocationdata and an image converter generates an image for display on a displaydevice. The multidimensional echolocation data stored in thepre-selected coordinate system of the echolocation data array is mappedto a specific location on the display device as a part of the imagegeneration.

DETAILED DESCRIPTION

New broad-beam technologies are systems and methods that allowmultidimensional (area or volume) echolocation data to be generated fromas few as one ultrasound beam. These technologies include generating anultrasound beam and transmitting it into a material under investigation,generating echo signals from resulting echoes, and processing the echosignals to produce echolocation data distributed in two or moredimensions.

Broad-beam technologies are less complex than prior art ultrasoundsystems and methods. For example, broad-beam systems and methods are notrestricted by the use of transmit lines, scan lines or receive lines,and broad-beam systems and methods can generate multidimensionalecholocation data from as few as one transmitted ultrasound beam.Dependence on transmit lines and receive lines is eliminated becausebroad-beam technologies do not require an assumption that echo sourcesare located along a one-dimensional line, such as transmit beam line 250and/or a receive line. Broad-beam systems and methods do not requiremultiple beam scanning or scan lines to generate a two dimensionalimage. Also, unlike the prior art, the resulting echolocation data mayresult from a single transmitted ultrasound beam that may be distributedover two dimensions. Using broad-beam systems and methods, a majority ofthe received echo signals may be used for image generation.

Unlike prior art embodiments, broad-beam systems and methods do notnecessarily depend on a transmitted ultrasound beam's shape or width todetermine the resolution of echolocation data. This independence arisesbecause broad-beam systems include no assumption that a transmittedultrasound beam is approximated by a transmit line or a columnsurrounding a transmit line. Generally, ultrasound beams (broad-beams)used in broad-beam systems and methods are wider than the finely focusedultrasound beam 170 used in the prior art.

Broad-beam systems and methods manipulate data differently than theprior art. Broad-beam systems and methods are based on multidimensionalde-convolution algorithms that convert echoes received at receivingtransducers into echolocation data, thereby generating multidimensionalecholocation data from a single transmitted ultrasound beam. Forexample, in one embodiment a de-convolution algorithm (calculation)affects a transform from two dimensional (time, ultrasound transducer)raw data to two dimensional (X,Y position) echolocation data. The twodimensional (time, ultrasound transducer) raw data is optionallygenerated using a single transmitted ultrasound beam, and withoutassuming a transmit line or a receive line. The two dimensionalecholocation data is distributed over an area requiring at least twospatial dimensions for representation. The data manipulation included inbroad-beam systems and methods is capable of using a single transmittedultrasound beam to produce a two-dimensional image configured fordisplay on a display device.

Broad-beam systems and methods take advantage of increases inmicro-processor power and advances in integrated circuit technologies.Current micro-processors are capable of performing broad-beam dataanalysis at a rate that is faster than the rate at which individualultrasound beams can be transmitted and received using prior artbeamforming technologies. While prior art technologies are restricted bythe pulse return time and the number of individual ultrasound beamsneeded to image an area, embodiments of the broad-beam approach leverageongoing advances in computing technology. Broad-beam systems and methodsachieve image generation rates that are not primarily limited by the useof narrowly focused ultrasound beams, as in the prior art.

For example, in a conventional system imaging to a depth of 200 mm, 128transmit/receive cycles require 33.3 milliseconds based on a speed ofsound of 1.54 mm/microsecond. This rate yields a frame rate ofapproximately 30 frames/second with an image resolution across the imagearea, perpendicular to the axis of element array 105, of 128 lines. Incomparison, using an embodiment of the invention to image the samedepth, a similar resolution can be obtained using five to seventransmit/receive cycles requiring a total of 1.3 to 1.8 milliseconds.These times limit the resulting frame rate to 769 and 549 frames/secondrespectively. In various embodiments, images, with image resolutions of128 lines as above, are obtained in less than 25, 17, 10, 5, or 2milliseconds.

Some embodiments of broad-beam technologies result in images thatminimize the occurrence of undesirable temporal anomalies associatedwith prior art scanning processes. The multidimensional echolocationdata derived from a broad-beam ultrasound beam is representative of asection of the material under investigation during the short period of apulse return time. Since this time is shorter then the time required toaccomplish a two-dimensional (multiple beam) scan in the prior art, theprobability of relative movement between the transducers and thematerial under investigation during the data collection is reducedrelative to the prior art.

Broad-beam systems and methods do not depend on the prior artapproximation that an ultrasound beam can be represented by a line, suchas beam line 250. Therefore, the resolution of resulting echolocationdata is not a function of distance from a focal point, such as prior artfocal points 230A-E. Broad-beams are typically wider, and capable ofimaging areas larger, than each of the focused beams of the prior art.

Since each broad-beam is capable of imaging an area larger than priorart ultrasound beams, the number of ultrasound beams required to image aspecific area is reduced relative to prior art. Because fewer, such asonly one, ultrasound beams are required, broad-beam systems and methodsmay use less power to image a material under investigation than priorsystems. Using less power decreases the amount of energy deposited inthe material under investigation, and decreases the amount ofelectricity required to generate each image. Reduced electricalrequirements may benefit devices using self-contained power sources,such as batteries.

Embodiments of broad-beam technology include an area forming™ process ofproducing, receiving, and analyzing an ultrasound beam wherein a set ofecholocation data, distributed over an area requiring two spatialdimensions for representation, is generated using as few as oneultrasound beam. The receive points at which echo detection occurs andecholocation data is generated may be anywhere within the probed region.The receive points optionally lie along a variable grid whosegranularity and regularity vary with position. Other embodiments ofbroad-beam technology include a volume forming process similar to areaforming except that three spatial dimensions are required to adequatelyrepresent the echolocation data generated using as few as one ultrasoundbeam. Area forming and volume forming are optionally combined withnon-spatial dimensions, such as time and velocity to achievemultidimensional forming processes.

FIG. 4 is a flow chart showing an overview of a broad-beam methodaccording to an embodiment of the invention and generally designated400. Method 400 begins with a broad-beam design step 410 that includesdetermination of the number and shapes of ultrasound beams (broad-beams)needed to image an area or volume. Within this step, desiredcharacteristics of at least one of the determined broad-beams arecalculated and parameters for the broad-beam's generation areestablished. The desired characteristics of each broad-beam may includefactors such as position, direction, width, intensity, dispersion, orthe like. The parameters may include voltages, aperture functions,excitation delays, and such.

In a transmit step 420, the broad-beam designed in step 410 is generatedand transmitted into a material under investigation. Transmit step 420includes generation of an electronic waveform using, for example, adigital or analog waveform generator. This waveform is coupled tomultiple channels, each of which may be independently delayed andamplified using devices such as a multi-channel delay generator and amulti-channel power amplifier. Typically, delay times are selectedresponsive to the desired shape, width and direction of the broad-beam.The amplified waveforms excite transducer elements 110 causing thebroad-beam to be transmitted into a material under investigation.

A receive step 430 uses transducer elements 110 to detect echoesproduced by the transmitted broad-beam. Transducer elements 110 generateelectronic signals responsive to the detected echoes. The resultingelectronic signals (analog channel data) are optionally filtered usingan analog filter and digitized, typically with a multi-channel A/Dconverter, to generate digital channel data. In one embodiment, thechannel data preferably includes both amplitude and phase information.In a store data step 440, the channel data is stored in a channel databuffer. This channel data buffer is located in memory such as RAM,magnetic media, optical media, or the like.

An echo area calculation step 450 includes manipulation of the storedchannel data using multidimensional de-convolution algorithms. Thesealgorithms are mathematical techniques that transform the channel datainto multidimensional echolocation data. Echo area calculation step 450can generate the multidimensional echolocation data without using thetransmit lines, receive lines, or scan lines that characterize the priorart.

Method 400 continues with a store echolocation data step 460 wherein theresulting echolocation data are stored using an echolocation data arraythat utilizes a pre-selected coordinate system. The echolocation data istypically located in memory such as RAM, magnetic media, optical media,or the like.

In a step 465, method 400 tests whether the data collection process iscomplete (e.g. the data required to generate the desired image has beencollected). If the data collection process is incomplete the methodreturns to broad-beam design step 410 wherein another broad-beam isdesigned. If, at step 465, the data collection process is complete animage may be generated in an optional generate image step 470 anddisplayed, on a display device such as a computer monitor, in anoptional display step 480.

In an alternative embodiment, broad beam design step 410 includescalculation of characteristics for several broad-beams. In thisembodiment a return to step 410, between steps 465 and 420 is optional.The method may proceed directly from step 465 to transmit step 420because the desired characteristics for a next broad-beam arepre-calculated in a prior instance of step 410.

FIG. 5 shows a broad-beam system according to an embodiment of theinvention and generally designated 500. A waveform generator 510, suchas a programmable pulse sequence generator or the like, is used togenerate electronic signals, such as electronic pulses 210, that arelater used to form a broad-beam ultrasound beam. The electronic signalsare individually delayed, through a delay device 515, in several signalchannels with a set of delays that are configured to generate anultrasound beam with characteristics designed in step 410 of FIG. 4. Theoutput of delay device 515 is coupled to a power amplifier 520, such asa power transistor, operational amplifier, high speed FET, or the like,where it is amplified and passed through a transmit/receive switch 525.Transmit/receive switch 525 optionally includes a multiplexer 527configured to couple input channels including signals received fromdelay device 515 to output channels for transmission to a transducerarray 530, which may be analogous to prior art element array 105.Transducer array 530 includes ultrasound transducer elements, such asultrasound transducer elements 110A-110H, that generate a broad-beam byconverting electrical signals received from transmit/receive switch 525to ultrasound pulses.

Transducer array 530 is configured to transmit the broad-beam into amaterial under investigation 535. The transmission of the broad-beamoccurs in step 420 of FIG. 4. Echoes are generated in material underinvestigation 535 through interactions between the broad-beam andultrasound reflective objects, such as tissue and bone. Transducer array530 receives the generated echoes and produces corresponding electricalsignals in step 430 of FIG. 4. These electrical signals, which aretypically analog electrical signals, are coupled throughtransmit/receive switch 525 to a variable gain amplifier 540, such as avoltage regulated operational amplifier, digitally controlled amplifier,amplifying transistor circuit, or the like.

After amplification, signals are passed through an optional analogfilter 545 to an A/D converter 550, where the amplified signals aredigitized. Analog filter 545 may be any analog filter known in the artsuch as a band-pass filter, a notch filter, or the like. A/D converter550 is typically a commercially available analog to digital converter,or the like.

The resulting digital data are stored, in step 440 (FIG. 4), in achannel data storage buffer 555 where they are operated on by signalprocessor 560. Channel data storage buffer 555 may be located in anystorage system known in the art. For example, channel data storagebuffer 555 is optionally located in electronic memory, such as RAM, ormagnetic or optical memory such as disc drives, compact disks, or thelike. The operations performed by signal processor 560 include echo areacalculations, of step 450 (FIG. 4), that transform time domain datastored in channel data storage buffer 555 to echolocation data, such asraw data or detected data, that is stored, in step 460 (FIG. 4), in anecholocation data storage 565. From echolocation data storage 565, datais optionally transferred to an additional data storage 570, or accessedby an image converter 575. Echolocation data storage 565 and additionaldata storage 570 may be any suitable store devices such as electronicmemory, magnetic or optical media, or the like. Image converter 575 isanalogous to “image scan converters” of the prior art, but mayadditionally operate on data generated using a single ultrasound beamrather than data generated using a “scan” including several ultrasoundbeams. In step 470 (FIG. 4), image converter 575 may use data stored inecholocation data storage 565, additional data storage 570, or both togenerate detected data or image data.

The image generation process may be analogous to prior art techniques ofimage generation using echolocation data generated through beam formingmethods. For example, a specific position in echolocation data storage565 is optionally mapped to a specific location on a display screen.Intensity and/or color of a position within the image may indicate theintensity or other characteristic of echoes detected from withinmaterial under investigation 535. This image is optionally shown, instep 480 (FIG. 4), on a display 580 such as an LCD screen, CRT screen,computer monitor, electronic display, or the like.

Data used by image converter 575 may result from a series of ultrasoundbeams or alternatively from a single ultrasound beam. Data in additionaldata storage 570 is coupled to other components of broad-beam system 500such as image converter 575, communications electronics 585 and userinterface electronics 590. Components of broad-beam system 500 arecontrolled and coordinated by control electronics 595 throughconnections not shown in FIG. 5. Control electronics 595 includemicroprocessors, DSPs, and optional computer code 596 configured tocontrol elements of broad-beam system 500 and execute methods of theinvention such as broad-beam process 400.

FIG. 6 is a flow chart illustrating broad-beam design step 410 accordingto an embodiment of the invention. In this embodiment, calculations areperformed using computer code 596 and may include, for example,mathematical models of ultrasound beam generation, propagation andechoing. In some instances lookup tables are used to speed thecalculation process. For example, if a user has indicated a specificdepth of analysis a desirable intensity is optionally determined from alookup table. Broad-beam design step 410 begins with a coveragedetermination step 610 in which the area (or volume) within materialunder investigation 535 to be investigated and the time period overwhich the investigation is to occur is determined. Coveragedetermination step 610 may be responsive to options selected by a userand the requirements of the current imaging (analysis) mode. Forexample, in a Doppler imaging mode the user may choose continuousmonitoring and a broad-beam characterized by a continuous series ofultrasound pulses. In another example, a user may choose to spotlight aregion within material under investigation 535 using a restricted fieldof view. The choice of a specific field of view is optionally used whencalculating a width of a generated broad-beam. For example, widths ofbroad-beams may be selected such that an integral number of broad-beamsfit, with 10% overlap, into a chosen field of view.

Also, coverage determination step 610 may determine a number ofbroad-beams required to image an area (or volume) within material underinvestigation 535. For example, in one embodiment coverage determinationstep 610 includes a calculation configured to simulate coverage in thefar field that determines that an area is best imaged using threebroad-beams displaced from each other using block-switching techniques.In other embodiments the calculation determines that an area is bestimaged using one, two or more broad-beams. When the user has selected amode of operation that includes several different broad-beams, repeatedimaging or continuous monitoring, coverage determination step 610 isoptionally performed once for each broad-beam.

Coverage determination step 610 is followed by a characteristicdetermination step 620 in which further characteristics of broad-beam(s)determined in coverage determination step 610 are specified. Thesecharacteristics include, but are not limited to, ultrasound frequencies,direction, dispersion, pulse shape, phase relationships, aperture,intensity, duration, repetition rate and/or other properties of anultrasound beam. The characteristics are typically dependent on theimaging mode of analysis being performed, the required resolution, andoptions selected by a user. For example, a continuous monitoring modemay require a broad-beam generated at a specific pulse rate, highresolution may require use of multiple ultrasound frequencies, and auser may choose to investigate a narrow region best probed by abroad-beam with low dispersion. In addition to the characteristicsdiscussed above, characteristic determination step 620 may includeselection of a coordinate system with which to represent the areacovered by the broad-beam and an origin of this coordinate system. Sucha coordinate system may be used to store echolocation data. Selection ofa coordinate system is optionally responsive to the shape of abroad-beam. Examples of possible coordinate systems are illustrated inFIG. 7.

Coverage determination step 610 and characteristic determination step620 are optionally responsive to resolution and dynamic rangerequirements. For example, in one embodiment these steps are responsiveto user input that specifies an image zoomed in on a specific area. Inanother embodiment these steps are responsive to user input thatspecifies a higher image resolution for part or all of an image. Inanother embodiment coverage determination step 610 includes adetermination that a single ultrasound beam should be generated butthat, for instance to enhance resolution, the echoes generated by thesingle ultrasound beam should be detected by several different sets ofreceive transducers in multiple transmit/receive cycles.

Coverage determination step 610 and characteristic determination step620 are optionally responsive to feedback generated in other steps ofthe invention. For example, in one embodiment, echolocation dataindicates that a region of the covered area is poorly imaged and thatthe poor imaging is caused by a highly reflective boundary disposedbetween the poorly imaged region and the closest of transducer elements110. In response to this feedback, coverage determination step 610 andcharacteristic determination step 620 include defining a steeredbroad-beam that probes the region from alternative ultrasoundtransducers that are not inline with the reflective boundary and theregion to be probed.

Broad-beam selection step 630 includes selection of a broad-beam fortransmission. The broad-beam is selected from those defined incharacteristic determination step 620. If several broad-beams have beencharacterized in characteristic determination step 620 then broad-beamselection step 630 is optionally performed more than once before thenext occurrence of characteristic determination step 620. In such a casebroad-beam selection step 630 is repeated after step 465 of FIG. 4.

Broad-beam design step 410 concludes with a calculate excitation step640. Calculate excitation step 640 includes determining the properphysical parameters required to generate the broad-beam selected inbroad-beam selection step 630. These physical parameters include, forexample, which transducer elements 110 to excite, electronic pulsevoltages, pulse delay times, multiplexer 527 settings, and/or the like.For example, in one embodiment a selected ultrasound beam, having aparticular desired shape and direction, requires use of a specific setof transducer elements 110, excited by a particular electronic waveformcharacterized by amplitudes, frequencies and phases, each of therequired set of transducer elements 110 being excited with anappropriate delay. The proper physical parameters are determined, forexample, using a mathematical model to calculate a voltage, waveform,and delay used for exciting a particular member of transducer elements110. In one embodiment the voltage is responsive to a distance into thematerial under investigation 535 the broad-beam is expected topenetrate.

FIGS. 7A-7C show embodiments (710A-710C) of a broad-beam 710 determinedin coverage determination step 610 and characteristic determination step620. FIG. 7A shows broad-beam 710A generated using a linear embodimentof transducer array 530. The area of an insonified region, generallydesignated 715A, is optionally represented by a radial (θ,R) coordinatesystem with an origin 720 located at the surface of transducer elements110. Points within insonified region 715 are identified by theirdistance (R) from an origin 720 and their angular coordinate (θ)relative to transducer array 530 or an axis, such as an axis 730 or anaxis 735. In alternative embodiments the focal point of broad-beam 710Bis located behind transducer array 530, rather than in front oftransducer elements 110 as shown in FIG. 2.

FIG. 7B shows broad-beam 710B generated using a curvilinear embodimentof transducer array 530. An insonified region, generally designated715B, is optionally represented by a radial coordinate system with anorigin 755 behind transducer array 530. This origin location providesinsonification of more area proximal to transducer elements 110 than anorigin location closer to transducer array 530 as shown in FIG. 7A. Thelocation of origin 755 behind transducer array 755 is optionallyindependent of the shape of transducer array 755. Embodiments of theinvention also include, but are not limited to, positioning origin 755and/or a focal point behind a linear embodiment of transducer array 530.

FIG. 7C shows broad-beam 710C that results in an insonified region,generally designated 715C. Insonified region 715C is more rectangular inshape than those generated by broad-beam 710A and broad-beam 710B, shownin FIGS. 7A and 7B, respectively. The region insonified by broad-beam710C may be preferably represented by a Cartesian (x,y) coordinatesystem 780 because of the region's rectangular shape.

In contrast with the prior art, where the maximum intensity is found atthe center of an ultrasound beam, the maximum intensity of a broad-beam,such as broad beam 710B or 710C, may be at points other than along thebeam's center. FIG. 7D shows a plot 790 of ultrasound intensity througha cross-section of broad-beam 710C as measured at a distance fromtransducer array 530, approximately equal to ½ the width of the beam'saperture. This cross-section is indicated by a dashed line 785 in FIG.7C. In some circumstance, the intensity profile of a broad-beamrepresents a more desirable energy distribution than those found in theprior art. For example, the energy distribution illustrated by plot 790is more evenly distributed over insonified region 715C than the energydistribution within a prior art ultrasound beam in the region of a focalpoint.

FIG. 8 shows details of an embodiment of transmit step 420 of FIG. 4. Inthis embodiment, step 420 includes a waveform generation step 810 inwhich waveform generator 510 is used to generate an electrical waveformwith characteristics calculated in broad-beam design step 410. Thegenerated waveform optionally includes a plurality of pulses of varyingfrequency or phase. In a signal delay step 820 the generated waveform isreproduced in several signal channels and delayed, using delay device515, by times determined in broad-beam design step 410. Waveforms ineach signal channel are amplified in an amplification step 830 usingpower amplifier 520. The amplified waveforms are coupled throughmultiplexer 527 in a multiplex step 840. Multiplexer 527 is set todirect the waveform in each signal channel to one or more member oftransducer elements 110 in transducer array 530. In sound generationstep 850, the directed waveforms cause transducer array 530 to generatebroad-beam 710, which is directed into material under investigation 535.Sound generation step 850 completes transmit step 420.

FIG. 9 shows details of an embodiment of receive step 430 of FIG. 4 inwhich echoes are detected and converted to digital data. In a set switchstep 910 transmit/receive switch 525 is set such that signals producedat transducer elements 110 are coupled through multiplexer 527 tovariable gain amplifier 540. In an echo detection step 920, echoes fromwithin material under investigation 535 are detected by members oftransducer elements 110 in transducer array 530. The members oftransducer elements 110 used for detection of echoes are optionallydifferent than the members of transducer elements 110 used to transmitbroad-beam 710. In various embodiments these two sets of transducerelements 110 are configured a number of ways. For example the sets maybe identical, interleaved, overlapped partially along transducer array530 or not overlapped along transducer array 530. The electronic signalsresulting from the detected echoes are coupled to variable gainamplifier 540 because transmit/receive switch 525 was set in set switchstep 910.

The electronic signals coupled to variable gain amplifier 540 areamplified in a variable amplification step 930. Variable amplificationstep 930 optionally includes feedback based on data obtained using aprior broad-beam 710. The feedback provides adaptive processing and canbe used to adjust signal within each channel such that the dynamic rangeof subsequent data manipulation steps are maximized. For example, in oneembodiment, if previous execution of variable amplification step 930resulted in the saturation of a specific channel, then amplification inthat channel is optionally reduced in a following execution of variableamplification step 930. The reduction, or adaptive front end gain, iscompensated for in later data manipulation that occurs afterdigitization of the amplified signal. In another embodiment, transducerelements 110 near the center of transducer array 530 are found tosystematically respond to echoes more strongly than transducers elements110 near an edge of transducer array 530. Variable amplification step930 optionally includes compensation for this systematic difference.

In an optional analog filtering step 940 the electronic signals,amplified in variable amplification step 930, are processed using analogfilter 545. This processing includes, for example, I/Q mixing, removalof unwanted frequencies and shifting of signals into frequency rangesmore suitable for further data manipulation.

In a data conversion step 950 the electronic signals, optionallyfiltered in analog filtering step 940, are digitized using A/D converter550. The generation of digital data completes receive step 430 (FIG. 4).In various embodiments data conversion step 950 occurs at alternativetimes within broad beam process 400. After the completion of receivestep 430 the resulting digital data is stored, in store data step 440(FIG. 4), in channel data storage buffer 555.

FIG. 10 shows an embodiment of a channel data array 1000 configured tohold the digital data stored in store data step 440. Channel data array1000 is stored in channel data storage buffer 555. A first axis 1010, ofChannel data array 1000, is indexed by echo receiving members oftransducer array 530. A second axis 1020 of channel data array 1000 isdivided into time channels. Values stored at each location in the arrayindicate the intensity and phase of echo signals detected by a specificmember of transducer array 530 at a specific time.

Channel data storage buffer 555 optionally includes several channel dataarray 1000. Additionally, the information stored in channel data array1000 may be used to average or sum received signals. In variousembodiments channel data array 1000 is configured to storemultidimensional data. For example, in one embodiment transducer array530 is a two dimensional array of transducer elements 110. In thisembodiment channel data array 1000 includes two axes representing thetwo dimensions of transducer array 530 and one axis representing timechannels.

Echo area calculation step 450 uses data stored in store data step 440to generate echolocation data indicating the positions and strengths ofecho sources within material under investigation 535. This generation ofecholocation data includes transformation of multidimensionaltime-channel data, within channel data array 1000, to multidimensionalpositional (echolocation) data. For example, in one embodimenttwo-dimensional time-channel data is transformed into echolocation datarepresented by two-dimensional spatial coordinates. The data transformof echo area calculation step 450 is performed using a variety ofalternative transform algorithms, examples of which are disclosedherein. These transforms are optionally used to generate two-dimensionalecholocation data using signals received as the result of a singlebroad-beam 710. In an alternative embodiment echo area calculation step450 is replace by an analogous echo volume calculation step including anadditional spatial dimension. Echo Volume calculation includes thegeneration of three-dimensional echolocation data using signals receivedas the result of a single broad-beam, the broad-beam covering a threedimensional volume.

FIGS. 11A and 11B show two embodiments of an echolocation data array1100 stored in echolocation data storage 565 and configured to storepositional data resulting from echo area calculation step 450. These twoembodiments employ different coordinate systems. As discussed in furtherdetail below, the more efficient coordinate system may be dependent on,among other factors, the shape of an individual ultrasound beam 710. Inmost instances, a more efficient coordinate system will overlay closelywith the area being insonified. For example, as shown in FIGS. 7A-7C,the area insonified by broad-beam 710A, broad-beam 710B and broad-beam710C are each preferably represented by different coordinate systemswith different origins. Use of a more efficient coordinate system mayincrease sampling efficiency and spatial resolution. Selection of apreferred coordinate system and echolocation data array 1100 may beresponsive to the shape of an ultrasound beam, such as broad-beam 710,and optionally occurs in steps 410, 440 or 450.

FIG. 11A shows an embodiment of echolocation data array 1100 using aCartesian coordinate system including a first axis 1110 indicating an Xcoordinate (position) and a second axis 1120 indicating a Y coordinate(position). FIG. 11B shows an alternative embodiment of echolocationdata array 1100 using a radial coordinate system including first axis1110 indicating an angle (θ) coordinate and second axis 1120 indicatinga radius coordinate. Alternative embodiments of echolocation data array1100 are represented by alternative coordinate systems. Additional data,not shown, is optionally used to relate first axis 1110 and second axis1120 to transducer array 530. For example, echolocation data array 1100is optionally characterized by vectors relating the origin of eachcoordinate system to a specific member of ultrasound transducer elements110.

FIGS. 12A and 12B illustrate how use of one coordinate system may bemore efficient than use of another coordinate system. FIGS. 12A and 12Bshow the embodiments of echolocation data array 1100 shown in FIGS. 11Aand 11B, respectively, overlaid on an ultrasound beam 1210. Ultrasoundbeam 1210 is an embodiment of broad-beam 710. FIG. 12A shows a Cartesiancoordinates system including, for the purposes of illustration, eleven“X” divisions separating data bins 1220. Data bins 1220 are justadequate to cover the far field, generally designated 1230. Because thespacing of data bins 1220 in the X dimension is the same in the nearfield, generally designated 1240, a number of data bins 1220 in nearfield 1240 are mapped to area that is not probed by ultrasound beam1210. These data bins 1220, not mapped to probed area, representinefficient sampling of the material under investigation 535.

In contrast, FIG. 12B shows use of a radial coordinates system torepresent the area insonified by ultrasound beam 1210. In the radialcoordinate system the size of data bins 1250 vary as a function of the“R” coordinate. Data points in this embodiment of echolocation dataarray 1100 are, therefore, more efficiently mapped to the area probed byultrasound beam 1210, than the embodiment of echolocation data array1100 shown in FIG. 12A. The variation of data bin 1250 size increasesefficiency because, as shown in FIG. 12B, a greater fraction of databins 1250 within data array 1100 fall within the area covered byultrasound beam 1210.

The granularity of data bins is dynamic. In some embodimentsecholocation data array 1100 represents a Nyquist sampled space whereinthe density of bins 1250 is varied such that the number of samples justsatisfies Nyquist criteria for un-aliased sampling throughout a regionof interest. In some embodiments the density of bins 1250 is varied suchthat the resolution of resulting echolocation data is greater in aspecific region. For example, in one embodiment a user specifies aparticular region where more image detail is desired. In response,broad-beams systems and methods use an echolocation data array 1100 withgreater density of bins 1250 in this region.

Some embodiments of the present invention include extrapolation andinterpolation between data bins 1250. For example, in one embodimentinterpolation is used in the far field, where each of data bins 1250represent a greater area, to increase the density of echolocation data.Optionally, less interpolation is used in the near field were thedensity of data bins 1250 is greater.

The resolution (sampling frequency) of channel data generated in receivestep 430 fundamentally limits the resolution of resulting echolocationdata as a result of the Nyquist theorem. However, the resolution of datagenerated in receive step 430 is optionally improved through signalaveraging or up-sampling techniques. Up-sampling techniques include theuse of additional data and optionally include feedback such thatadditional data is collected in regions where improved resolution ismost needed.

FIGS. 13 through 15 are used to show embodiments of echo areacalculation step 450 (FIG. 4). FIG. 13 shows propagation of ultrasoundbetween transducer elements 110A-110S, and ultrasound reflecting objectswithin material under investigation 535. FIG. 14 shows channel dataproduced from detected echoes. And, FIG. 15 shows echolocation datagenerated using the channel data shown in FIG. 14.

In several embodiments of echo area calculation step 450 including datatransform methods it is assumed that the primary contributor to detectedechoes from each location within the material under investigation 535 isthe member of transducer elements 110 closest to that location. Thiselement is referred to as the main contributing element (MCE).Typically, the member of transducer elements 110 that is closest to alocation is the MCE for that particular location, and any ultrasoundreflective object at that location. However, the identity of the MCE mayalso be dependant on the direction of broad-beam 710 and the shape oftransducer array 530. In such a case, the MCE may not be the transducerelement 110 closest to the particular location. The data transformmethods, of echo area calculation step 450 (FIG. 4), optionally includebroad-beam 710 direction, transducer array 530 geometry, feedback, aswell as other factors for determining an MCE that is not the closestmember of transducer elements 110 to an ultrasound reflective object.

FIG. 13A shows ultrasound 1305 transmitted from a single transducerelement 110G. Ultrasound 1305 travels through material underinvestigation 535 (not shown) until it strikes an ultrasound reflectingobject 1310A. Transducer element 110G is the closest of transducerelements 110A-110S to ultrasound reflecting object 1310A, and istherefore considered to be the MCE for reflecting object 1310A. Atultrasound reflecting object 1310A, ultrasound 1305 generates ultrasoundechoes 1315 of which ultrasound echoes 1315A-1315F are shown. Ultrasoundechoes 1315 propagate back to transducer elements 110A-110S where theyare detected.

Although FIG. 13A shows ultrasound 1305 transmitted from one transducerelement 110G (the MCE), in most embodiments ultrasound is transmittedfrom a plurality of transducer elements 110A-110S during the formationof broad-beam 710. FIG. 13B shows ultrasound 1330 generated by a singletransducer element 110Q, which is the MCE for an ultrasound reflectingobject 1310B. Echoes 1340, of which ultrasound echoes 1340A-1340F areshown, generated at reflecting object 1310B travel back to and aredetected by transducer elements 110A-110S.

FIG. 14 shows an embodiment of channel data array 1000 including datagenerated by ultrasound 1305 and ultrasound 1330 shown in FIG. 13. Eachof columns 1410A-1410S in channel data array 1000 represents signal(s)detected at one of transducer elements 110A-110S. Each of rows1420A-1420U in channel data array 1000 includes the signal detectedduring a specific time period. In FIG. 14 data elements 1430, thatincluded data generated by detection of echoes 1315 and 1340, are thosedata elements 1430 that intersect a data location line 1440A or a datalocation line 1440B, respectively. Thus, ultrasound echoes generatedfrom a reflective object, such as ultrasound reflective object 1310,within material under investigation 535 results in data that lies alonga line, such as data location lines 1440A or 1440B. Data location lines1440A and 1440B can be calculated from first principles of physics andgeometry using a known geometry of transducer array 530 and the speed ofsound within material under investigation 535. Data location lines 1440Aand 1440B do not intersect the MCE, transducer element 110G, nortypically any other transducer element 110. In practice, material underinvestigation 535 includes numerous ultrasound reflective objects 1310,and channel data array 1000 includes data generated by each.

In embodiments of echo area calculation step 450, echolocation data iscalculated by summing data along a line such as data location line1440A, data location line 1440B, or the like. For example, summation ofdata along data location line 1440B generates a result indicative of themagnitude of echoes 1315 generated at the position occupied byultrasound reflecting object 1310B and represented by a data bin, suchas data bin 1220 or data bin 1240. The sum is stored in therepresentative data bin. A similar summation is optionally performed foreach data bin in echolocation data array 1100. Through multiplesummations echolocation data array 1100 is populated with echolocationdata representing ultrasound reflective objects within material underinvestigation 535.

FIG. 15 shows an embodiment of echolocation data array 1100 includingecholocation data bins 1520. Each of echolocation data bins 1520 isassociated with a unique line, such as data location line 1440A, inchannel data array 1000 as shown in FIG. 14. Data along the unique lineis summed to calculate the magnitude of echo generation that occurred atthe physical locations represented by each of data bins 1520. Thissummation is optionally performed for all of data bins 1520 and thus canbe used to calculate echolocation data over the entire echolocation dataarray 1100.

FIG. 16 shows a data transform method included in an embodiment of echoarea calculation step 450. This embodiment includes a select elementstep 1610 in which one of echolocation data bins 1520, withinecholocation data array 1100, is selected. Typically, selection of eachof echolocation data bins 1520 is accomplished by traversingecholocation data array 1100 in a systematic fashion. Select elementstep 1610 is followed by a determine line step 1620 in which the uniqueline in channel data array 1100 associated with the selectedecholocation data bins 1520 is determined. Determination is accomplishedby calculating the line from geometric principles, using a look-up tablewith previously calculated lines, or the like. Determination may occurbefore or during echo area calculation step 450. In various embodimentsdetermination occurs prior to or during broad-beam design step 410. Inalternative embodiments, determination occurs during steps 420, 430,and/or 440 (FIG. 4). Determine line step 1620 is followed by a sum datastep 1630 that includes summation of data from data elements 1430 thatintersect the line determined in determine line step 1620. In oneembodiment sum data step 1630 includes a simple addition of data. Inalternative embodiments sum data step 1630 includes use of weightingfunctions, matrix manipulation, extrapolation, interpolation, or likemathematical techniques. In one embodiment sum data step 1630 isfacilitated by firmware within control electronics 595. In a storeresult step 1640 the result of the summation of step 1630 is stored inthe data element selected in select element step 1610.

Steps 1610 through 1640 are optionally repeated for all echolocationdata bins 1520 in echolocation data array 1100. FIG. 15 shows two sets(1550 and 1560) of echolocation data bins 1520 including non-zero valuesresulting from summation along data location lines 1440A and 1440B usingthe method shown in FIG. 16. Each set (1550 and 1560) of echolocationdata bins 1520 typically include echolocation data bins 1520 withdiffering non-zero values. In several embodiments one or more of steps1610 through 1640 are performed as parallel processes.

Alternative embodiments of echo area calculation step 450 includealternative methods of data transformation. These methods use, forexample, calculations performed in the frequency domain, use of phaserelationships between received signals, use of apodization functions toweigh contributions of each of transducer elements 110, feedbackmechanisms, correlation analysis and consideration of transmittingtransducer elements 110 other than the MCE. These other transducerelements 110 are used to improve both the quality and speed of thetransformation from channel data to echolocation data.

In one embodiment, echo area calculation step 450 includes use of anapodization function to weigh contributions of each transducer element110. Weighting may be desirable because those transducer elements 110closer to an MCE receive stronger echoes from a particular reflectiveobject 1310 than do transducer elements 110 further from the MCE.Signals detected at an MCE and the transducer elements 110 nearby aretherefore given greater weight than transducer elements 110 further fromthe MCE.

FIG. 17 shows three alternative apodization functions according toembodiments of the invention. Graph 1710 illustrates these threealternative apodization functions, designated 1720, 1730 and 1740. Forexample, if transducer element 110G is the MCE for one of data elements1430 selected in select element step 1610 of FIG. 16, then apodizationfunction 1720 is used in sum data step 1630 such that the resulting sumincludes a greater contribution from transducer elements 110 neartransducer element 110G. Likewise, for summations wherein transducerelements 110K and 110S are the MCE, apodization functions represented bylines 1730 and 1740 are optionally used.

In alternative embodiments, echo area calculation step 450 is performedat least in part in the frequency domain. Data is converted usinginvertible transforms, for example sine transform, Fourier transform,wavelet transform, or the like.

In some embodiments of echo area calculation step 450 phaserelationships between received signals are used to distinguish betweenthose signals resulting from ultrasound transmitted by the MCE and thosesignals resulting from secondary contributing elements (SCEs). SCEs aretransducer elements 110, other than the MCE, that contribute to signalarising from a given ultrasound reflective object, such as ultrasoundreflective object 1310.

FIG. 18 shows ultrasound 1810 and 1305 transmitted from transducerelements 110F and 110G and striking ultrasound reflective object 1310A.Transducer element 110G is considered the MCE for ultrasound reflectiveobject 1310A because it is the closest member of transducer elements110. In alternative embodiments a closely grouped set of transducers aretreated jointly as an MCE. Other transducer elements 110, such astransducer element 110F, also generate ultrasound that can reachreflective object 1310A. In this example, transducer element 110F is aSCE. Ultrasound must travel further from these (SCE) transducer elements110 than from the MCE transducer elements 110, before reachingultrasound reflective object 1310A. As with the ultrasound generated bythe MCE, ultrasound from the SCEs generates echoes when strikingultrasound reflective object 1310A. Some of these echoes are detected attransducer array 530.

FIG. 19 shows locations of signals generated by SCE transducer element10F in channel data array 1000. These signals lay along a data locationline 1910 similar to data location line 1440A, but at a slightly latertime. The time difference between data location lines 1440A and 1910 isdue to the difference in time required for ultrasound to travel toultrasound reflective object 1310A from transducer element 110F and fromtransducer element 110G. It is desirable to distinguish data resultingfrom SCEs from data resulting from an MCE. Although signal from the MCEis typically stronger than signal resulting from SCEs (due to the longerdistance ultrasound must travel), the signal from the SCEs isadditionally differentiated by a phase difference that results from thedifference in distance traveled. Considering signals only with specificphases allows signals resulting from SCEs to be separated by filtering.For example, in one embodiment SCE signal is filtered out by more than10 dB and in some embodiments by more than 38 dB.

In various embodiments, data resulting from SCEs are used to improveresults obtained in echo area calculation step 450. For example, in someembodiments, data resulting from an SCE is added to data resulting froman MCE. Thus, data laying along data location line 1910, as shown inFIG. 19, is added to data lying along data location line 1440A. The datalying along data location line 1910 includes data resulting fromultrasound generated at (SCE) transducer element 10F and echoed fromreflecting object 1310A. After a phase adjustment and weighting thisdata may constructively add to data lying along data location line1440A, and thus improve the signal to noise ratio of echolocation dataindicating the presence of reflecting object 1310A. Typically, SCEsclosest to an MCE are given more weight than SCEs further away. Forexample, one embodiment uses a Chi Squared weighting distribution,centered on the MCE to determine weighting of neighboring SCEs. Inanother embodiment the weighting distribution is responsive to feedbackalgorithms that reduce the weight of SCEs whose signal in channel dataarray 1000 overlap with a strong MCE signal.

In other embodiments signal resulting from an SCE is subtracted fromsignal resulting from an MCE. For example, if a large MCE signal isdetected along data location line 1440A as shown in FIG. 19, then acorrespondingly large SCE signal will be expected along data locationline 1910. Since the corresponding SCE signal is predictable andapproximate values can be calculated as a function of the MCE signal,the calculated values can be subtracted from channel data values storedin data elements 1430 before these data values are used to calculatevalues for other echolocation data bins 1520. Consideration of dataresulting from SCEs to improve echo area calculations optionally occuras part of sum data step 1630 (FIG. 16).

Several embodiments of echo area calculation step 450 use feedback. Forexample, in one embodiment calculated echolocation data is processed ina “reverse” data transform using techniques that produce a simulatedecho signal (simulated channel data) based on the calculatedecholocation data. This reverse transform produces a simulation of thechannel data that would be expected if the calculation of echolocationdata was optimal. The reverse transform is optionally preformed usingray-tracing methods known in the art. The simulated channel data iscompared with the actual echo data stored in channel data array 1000.Similarity between these two data sets is indicative of the quality ofthe calculation used to produce the echolocation data. In an optionaliterative process, the calculation of echolocation data is repeatedusing varying parameters responsive to this similarity. These parametersmay include different weighting factors, apodization functions or SCEs,manipulated to optimize the similarity between the data in channel dataarray 1000 and simulated echo signals.

In other embodiments feedback includes use of echolocation data tocontrol broad beam design step 410. For example, in one embodiment thedirection of an ultrasound beam designed in step 410 is responsive tothe location of reflective boundaries in material under investigation535. In other examples, the focus, width, frequency, intensity, ornumber of beams designed in step 410 are responsive to calculatedecholocation data.

Several embodiments of echo area calculation step 450 include datatransforms employing correlation analysis. Correlation methods are knownin the data analysis art and are useful for enhancing similarities andmaking comparisons between data. Correlation is particularly useful forcomparing data that systematically differs, for example by a change inphase. A cross-correlation analysis of two data sets, differing by aconstant degree along one coordinate, identifies the constant differenceand the similarity of the data after accounting for that difference. Anauto-correlation analysis of a data set exemplifies periodic orrepetitive signals within the data.

FIG. 20 shows an embodiment of echo area calculation step 450 thatincludes a cross-correlation method used to identify components of SCEdata that correlate well with MCE data. In a calculate cross-correlationstep 2010 data laying along a line, such as line data location 1440A(FIG. 14), associated with an MCE is cross-correlated with data layingalong a line, such as data location line 1910 (FIG. 19), associated withan SCE. Each of these sets of data is optionally pre-processed using afunction such as apodization function 1720. The cross-correlationgenerates a correlation data set that can be expressed as a function ofphase difference verses similarity between the two data sets. In acalculate phase difference step 2020 the expected phase differencebetween the MCE data and the SCE data is calculated based on a knowngeometrical relationship between the MCE and the SCE. In a look-up step2030 this calculated phase difference is used to look-up a similarityvalue in the correlation data set generated by the cross-correlation, atthat specific phase difference, in the correlation data set. Thesimilarity value, corresponding to the phase difference calculated inphase difference step 2020, is indicative of how useful the SCE data canbe in improving the signal to noise ratio of the MCE data because moresimilar SCE data is more likely to constructively add to the MCE data.In a decision step 2040 the similarity value is compared with apredetermined threshold. If the similarity value is greater than thethreshold then the SCE data is added to the MCE data in an add data step2050. If, in step 2040, the similarity value is found to be less thanthe predetermined threshold, computer code 596 determines, in a decisionstep 2060, if further analysis of the particular SCE data set iswarranted. Further analysis may be warranted if, for example, nearbySCEs are yet to be examined or if a user has requested additionalimprovement in the signal to noise ratio. If not, the analysis of thisparticular SCE data set is concluded. If step 2060 determines thatfurther analysis is warranted then the SCE data set is processed in anoptional filter step 2070. The processing in step 2070 includesfiltering, truncation or similar means designed to enhance thecomponents of the SCE data set that correlate well with the MCE dataset. For example, in one embodiment an alternative function, such asapodization function 1740 is applied to the SCE data set. The stepsshown in FIG. 20 are optionally applied to more than one SCE data set.

Echolocation data generated using alternative embodiments of echo areacalculation step 450 are optionally compared, and the comparison may beused to determine the consistency of calculations or to providefeedback. For example, in one embodiment two repetitions of echo areacalculation step 450 include consideration of different SCEs. Theaccuracy of these calculations is checked by comparing the results ofeach repetition. The closer the results the more likely the use of SCEsis producing an accurate result. In another example, echolocation datacalculated using two different embodiments of echo area calculation step450 are found to be significantly different. These differences are usedas feedback affecting other steps in the broad-beam technology. Forexample, irreproducibility of echolocation data in a specific region isoptionally used to provide feedback to broad-beam design step 410 suchthat a characteristic (intensity, frequency, direction, etc.) of abroad-beam probing that region is modified.

Data stored in echolocation data array 1100 is optionally used ingenerate image step 470 (FIG. 4) generate images of material underinvestigation 535 that can be displayed to a user. This generation anddisplay is accomplished using image converter 575 and display 580,respectively. Since two dimensional data can be generated from a singleultrasound beam using broad-beam techniques a two dimensional image canbe generated from a single ultrasound beam. In various embodiments thiscapability increases the image frame rate relative to prior art methodsbecause an image is produced in a time limited by a single pulse returntime, or optionally the return time of a few pulses (i.e. <5, <10, <20,<40 or <64), rather than the many (i.e. >100) pulse return times of theprior art. Benefits of generating an image from a single ultrasound beaminclude possibly reducing jitter in the resulting image because,relative to the prior art, there is less time for relative movementbetween transducer array 530 and material under investigation 535 duringthe period data is collected. Generating an image from a singleultrasound beam may also reduce the amount of ultrasound energy directedinto material under investigation 535 and the amount of electrical powerrequired to generate an image.

From the description of the various embodiments of the process andapparatus set forth herein, it will be apparent to one of ordinary skillin the art that variations and additions to the embodiments can be madewithout departing from the principles of the present invention. Forexample, transducer elements 110 can be replaced by alternativeultrasound generating elements and transmit/receive switch 515 can bereplaced by separate transmit and receive switches. The number oftransducer elements 110 shown in the figures is not meant to belimiting. Typical embodiments include larger numbers of transducerelements 110. Likewise, the resolution of shown data arrays is selectedfor illustrative purposes only. Typical embodiments include data arrayswith larger numbers of data bins.

Broad-beam technology is applicable to systems configured to use botharea forming and conventional beam forming. Some embodiments includemeans for switching between theses two approaches. For example, areaforming may be used to survey and area and conventional beam formingtechniques may be used to focus energy onto a specific area of interest.In some embodiments, including two dimensional transducer arrays, areaforming is used at the same time as conventional beam formingtechniques. For example, one set of transducer elements may be used forarea forming while another set of transducer elements may be used forconventional beam forming. In another example, area forming may be usedto gather data in one spatial dimension while conventional beam formingis used to gather data in an other spatial dimension. An ultrasound beammay be configured for area forming in one dimension and conventionalbeam forming in another dimension. In these examples, more than onemethod of echolocation is performed at the same time, each methodoptionally being associated with a specific spatial dimension.

Broad-beam technology is applicable to any system limited by the use ofphased arrays to scan a focused beam over an area or volume. Thesesystems may include sonic systems such as sonar, as well aselectromagnetic systems such as radar. Embodiments of broad-beamtechnology are used with two dimensional transducer arrays. In theseembodiments echo volume calculations replace echo area calculations andthe transform of step 450 includes conversion of a three dimensional(Transducer, Transducer, Time) array of echo data to a three dimensional(x, y, z) echolocation data array. In one embodiment a single threedimensional ultrasound beam is used to perform volume forming and thusproduce echolocation data covering a volume in space.

What is claimed is:
 1. A method of probing a material underinvestigation comprising the steps of: using a plurality of transducersto transmit a single ultrasound beam into the material underinvestigation, the single ultrasound beam including components generatedby each transducer in the plurality of transducers; receiving echoesgenerated by interactions between the single ultrasound beam and thematerial under investigation; generating first data from the receivedechoes, the first data having values that include phase and magnitudeinformation, the values of the first data associated with a timedimension and distributed over at least one spatial dimension; using thephase or magnitude information to identify a subset of distinguishedechoes, among the received echoes, resulting from ultrasound beamcomponents generated by a subset of transducers in the plurality oftransducers; and transforming the distinguished echoes into second data,the second data having values distributed over at least one more spatialdimension than the first data.
 2. The method of claim 1, wherein themagnitude information is used to distinguish echoes among the receivedechoes.
 3. The method of claim 1, wherein both the magnitude and phaseinformation are used to distinguish echoes among the received echoes. 4.The method of claim 1, wherein the phase information is used todistinguish echoes among the received echoes.
 5. The method of claim 4,wherein the ultrasound beam is configured to probe a region of interestincluding two or more spatial dimensions.
 6. The method of claim 5,further including a step of transmitting an additional ultrasound beaminto the material under investigation, the additional beam beingconfigured to probe a second region of interest overlapping the regionof interest including two or more spatial dimensions.
 7. The method ofclaim 5, further including the steps of: transmitting an additionalultrasound beam into the material under investigation to probe a secondregion of interest overlapping the region of interest including two ormore spatial dimensions; receiving second echoes generated byinteractions between the additional ultrasound beam and the materialunder investigation; generating third data using the received secondechoes; and generating an image using both the second data and the thirddata.
 8. The method of claim 4, further including a step of configuringthe single ultrasound beam responsive to an imaging mode.
 9. The methodof claim 4, further including the steps of: generating electronicsignals from the received echoes using receiving transducers; andamplifying the generated electronic signals using a weighting functionwith a factor responsive to an identity of a member of a set ofreceiving transducers.
 10. The method of claim 9, wherein the weightingfunction is responsive to the identity of a main contributing element.11. The method of claim 1, wherein the step of transforming the firstdata includes a multidimensional data transform.
 12. A method of probinga material under investigation comprising the steps of: transmitting asingle ultrasound beam into the material under investigation; receivingechoes generated by interactions between the single ultrasound beam andthe material under investigation; generating first data from thereceived echoes, the first data having a value that includes phase andmagnitude information, the value of the first data associated with timeand at least a first spatial dimension; and transforming a portion ofthe first data into second data using a transform that produces seconddata distributed over at least a second spatial dimension and a thirdspatial dimension, the transform using the phase or magnitudeinformation to select the portion of first data to be transformed. 13.The method of claim 12, wherein both the magnitude and phase informationare used to distinguish echoes among the received echoes.
 14. The methodof claim 12, wherein the phase information is used to distinguish echoesamong the received echoes.
 15. The method of claim 14, wherein the firstspatial dimension is the same as the second spatial dimension.
 16. Themethod of claim 14, further including a step of determiningcharacteristics of an ultrasound beam configured to analyze an areawithin the material under investigation.
 17. The method of claim 12,further including a step of determining an area to be probed by thesingle ultrasound beam, the second data being distributed over the area.18. The method of claim 12, wherein the transform includes determining adata location line using the location of a main contributing element.19. The method of claim 18, wherein the data location line is curved.20. The method of claim 18, wherein the data location line does notintersect the main contributing element.
 21. The method of claim 12,wherein the step of transforming the first data includes a transformthat uses correlation analysis.
 22. The method of claim 12, wherein thestep of transforming the first data includes determination of a maincontributing element.
 23. A method of probing a material underinvestigation comprising the steps of: transmitting a single ultrasoundbeam into the material under investigation; receiving echoes generatedby interactions between the transmitted single ultrasound beam and thematerial under investigation; generating first data using the receivedechoes, the first data having values associated with time and a numberof positions in a first spatial dimension, the number of positions beingat least 64 and the association with the number of positions beingindependent of the association with time; and transforming the firstdata into second data having values associated with at least the firstspatial dimension and a second spatial dimension.
 24. The method ofclaim 23, wherein the number of positions is at least
 128. 25. Themethod of claim 23, wherein the number of positions is at least
 256. 26.The method of claim 23, further including the step of receiving secondechoes generated by interactions between a second ultrasound beam andthe material under investigation.
 27. The method of claim 26, furtherincluding the step of generating third data using the received secondechoes, any combination of the first data and the third data having thesame dimensionality as the first data.
 28. The method of claim 23,wherein the second data is echolocation data.
 29. A method of probing amaterial under investigation comprising: transmitting at least twooverlapping ultrasound beams into the material under investigationwherein the at least two overlapping ultrasound beams are displaced inat least one spatial dimension; receiving echoes generated byinteractions between the at least two overlapping ultrasound beams andthe material under investigation; generating data from the receivedechoes, the data having a value that includes magnitude and phaseinformation, the value of the data associated with the at least onespatial dimension; performing receive beam formation wherein identicalreceive beams are formed from the at least two overlapping ultrasoundbeams; and combining the generated data from the received echoes priorto receive beam formation, wherein the combining comprises adjusting themagnitude and phase of the generated data.
 30. The method of claim 29wherein the at least two overlapping ultrasound beams are focused. 31.The method of claim 29 wherein the at least two overlapping ultrasoundbeams are partially focused.
 32. The method of claim 29 wherein the atleast two overlapping ultrasound beams are unfocused.
 33. The method ofclaim 29 wherein the at least one spatial dimension is azimuth.
 34. Themethod of claim 29 wherein the at least one spatial dimension is azimuthangle.
 35. The method of claim 29 wherein the at least one spatialdimension is the combination of azimuth and azimuth angle.
 36. Themethod of claim 29 wherein the at least one spatial dimension iselevation.
 37. The method of claim 29 wherein the at least one spatialdimension is elevation angle.
 38. The method of claim 29 wherein the atleast one spatial dimension is the combination of elevation andelevation angle.
 39. The method of claim 29 wherein adjusting themagnitude and phase of the data varies with depth.
 40. The method ofclaim 29 wherein adjusting the magnitude and phase of the data isperformed in the at least one spatial dimension directly.
 41. The methodof claim 29 wherein adjusting the magnitude and phase of the data isperformed in a suitable linear transformation of the at least onespatial dimension.
 42. The method of claim 41 wherein the suitablelinear transformation is a Fourier transform.
 43. A method of probing amaterial under investigation comprising: transmitting at least twooverlapping ultrasound beams into the material under investigationwherein the at least two overlapping ultrasound beams are displaced inat least one spatial dimension; receiving echoes generated byinteractions between the at least two overlapping ultrasound beams andthe material under investigation; generating data from the receivedechoes, the data having a value that includes magnitude and phaseinformation, the value of the data associated with the at least onespatial dimension; performing receive beam formation wherein identicalreceive beams are formed from the at least two overlapping ultrasoundbeams; and combining the generated data from the received echoessubsequent to receive beam formation, wherein the combining comprisesadjusting the magnitude and phase of the generated data.
 44. The methodof claim 43 wherein the at least two overlapping ultrasound beams arefocused.
 45. The method of claim 43 wherein the at least two overlappingultrasound beams are partially focused.
 46. The method of claim 43wherein the at least two overlapping ultrasound beams are unfocused. 47.The method of claim 43 wherein the at least one spatial dimension isazimuth.
 48. The method of claim 43 wherein the at least one spatialdimension is azimuth angle.
 49. The method of claim 43 wherein the atleast one spatial dimension is the combination of azimuth and azimuthangle.
 50. The method of claim 43 wherein the at least one spatialdimension is elevation.
 51. The method of claim 43 wherein the at leastone spatial dimension is elevation angle.
 52. The method of claim 43wherein the at least one spatial dimension is the combination ofelevation and elevation angle.
 53. The method of claim 43 whereinadjusting the magnitude and phase of the data varies with depth.
 54. Themethod of claim 43 wherein adjusting the magnitude and phase of the datais performed in the at least one spatial dimension directly.
 55. Themethod of claim 43 wherein adjusting the magnitude and phase of the datais performed in a suitable linear transformation of the at least onespatial dimension.
 56. The method of claim 55 wherein the suitablelinear transformation is a Fourier transform.